1. Field of the Disclosure
The following is directed to crucibles, and more particularly, a crucible having a monolithic body comprising silicon oxynitride.
2. Description of the Related Art
Certain processes of forming single crystal materials require vessels or crucibles to contain a significant quantity of molten material, while the crystal forming process is completed. For example, the Czochralski process pulls and forms a crystalline material from a crucible containing the melted material, wherein during the pulling process, the material is solidified and crystallized into an ingot, or large crystalline mass that can be further processed. In fact, silicon ingots are generally formed using one of three methods: (1) pulling an ingot from melt, (e.g., the Czochralski process); (2) solidifying a melt in a crucible by directional solidification techniques; or (3) pouring a melt from a crucible into a mold using casting techniques.
In a directional solidification process, silicon is typically melted in the crucible and directionally solidified in the same crucible. In this case, there is contact between the silicon melt and the crucible, as well as contact between the solidified silicon ingot and the crucible. In a casting process, the silicon is melted in a crucible and the melt is then poured from the crucible into a mold, where the silicon solidifies. The casting process can have contact between the melt and the crucible, the melt and the mold (although minimal), and the mold and the solidified ingot.
Still, a host of problems plague the industry when using crucibles in such capacities, including for example, particle generation and contamination concerns from the crucible, chemical reactions between the melt material and the crucible, proper wetting characteristics between the crucible and the melt material, release of solidified material from the crucible, thermal shock and cracking of the crucibles. In fact, it is a typical industry practice to use the crucible once to form a single ingot, and discard the crucible because it is destroyed or significantly compromised.
Silica remains the material of choice for crucible and mold applications because it is readily available in high purity form, and minimizes contamination in processing of silicon ingots. Moreover, such conventional quartz crucibles may have coatings of silicon nitride. Still, such conventional constructions are still subject to the problems noted above.
The industry continues to demand improved crucibles for holding melt materials and improving processes for forming single crystal materials.